CN1084479C - Timing method and device based on GPS signals - Google Patents

Abstract

A timing method based on GPS signals and a device using the method. This method introduces a binary voltage control table with phase difference change value and phase difference change rate as independent variables, and comprehensively considers adjusting the voltage value of the crystal, which can solve the SA interference and the frequency drift of the voltage-controlled crystal in the case of using a three-stage crystal. and frequency jitter problems, which greatly reduces the cost of the equipment and simplifies the structure.

Description

A timing method and device based on GPS signals

The present invention relates to the technology of providing accurate clock in the field of communication, more specifically, relates to a timing method and device based on GPS.

The U.S. Department of Defense established the global timing and positioning navigation satellite system (NAVSTAR GPS, hereinafter referred to as the GPS system) to provide people with the possibility of precise timing and positioning at any time and anywhere. However, the U.S. government deliberately added selective interference (SELECTIVE AVAILABLY, so called S.A. interference) to the signal transmitted by the satellite, which greatly reduced the timing and positioning accuracy obtained by ordinary users, and the timing accuracy dropped to more than ±150ns. Large companies in various countries have correspondingly developed various GPS receiving devices to extract a relatively stable output from satellite signals mixed with S.A. interference, among which HP58503 GPS time and frequency standard receiver of Hewlett-Packard Company has been smoothed for a long time (one hour) To filter out S.A. interference and achieve better results. However, this solution requires an expensive long-term stable crystal (above the second level) in order to effectively use long-term smoothing filtering to filter out S.A. interference, otherwise if the crystal is unstable (for example, a third-level crystal is used), one hour The frequency drift of the internal crystal itself is already considerable, and it is impossible to perform long-term smoothing and filtering; this scheme also requires correspondingly complex crystal peripheral circuits to make the crystal work normally; in addition, in order to perform long-term smoothing and filtering, a large-capacity memory is required In order to store the data recorded for a long time, and when the satellite signal quality suddenly deteriorates and then recovers after a period of time, since the program averages the long-term recorded data, the recorded data when the satellite signal quality deteriorates will also be in the long-term It is still used as valid data for a period of time, making it take a long time for the device to restore stable output.

The purpose of the present invention is exactly to overcome above-mentioned shortcoming, provide a kind of body is low, simple in structure, can capture GPS signal rapidly, and the situation that recovers again after satellite signal deteriorates recovers rapidly the timing method and equipment based on GPS signal of stable output.

For realizing the purpose of the present invention, one aspect of the present invention: a kind of timing method based on GPS signal, comprising comparing the phase difference of each GPS pulse received and the local frequency division pulse, and storing this phase difference, it is characterized in that according to effective Filter out S.A. interference and adjust the crystal in time Requirements Set a data storage capacity N, after storing N phase differences, smooth the data, adjust the crystal, smooth the data, adjust the crystal The process includes the following main steps:

(1) Calculate the average value of the N stored phase differences to obtain an average phase difference, and store the average phase difference;

(2) comparing the average phase difference with a preset standard phase difference to obtain a phase difference change value E;

(3) Comparing the average phase difference obtained this time with the average phase difference stored last time to obtain the phase difference change rate EC;

(4) According to the phase difference change value and the phase difference change rate, and the pre-stored binary voltage control table with the phase difference change value and the phase difference change rate as independent variables, determine the crystal control voltage difference that should be applied ΔU;

(5) Add the crystal control voltage difference ΔU to the current control voltage to adjust the local second pulse.

Another aspect of the present invention: a timing method based on GPS signals, including comparing the phase difference between each received GPS pulse and the local frequency-divided pulse, and storing the phase difference, characterized in that it is based on effective filtering of S.A. interference and timely The requirement for adjusting the crystal is to set a data storage capacity N. After storing N phase differences, smooth the data and adjust the crystal. The process of smoothing the data and adjusting the crystal includes the following main steps:

(1) Calculate the average value of the N stored phase differences to obtain an average phase difference, and store the average phase difference;

(2) comparing the average phase difference with a preset standard phase difference to obtain a phase difference change value E;

(3) Comparing the average phase difference obtained this time with the average phase difference stored last time to obtain the phase difference change rate EC;

(4) The crystal voltage control difference is directly obtained from the formula ΔU=λ ₁ E+λ ₂ EC .

(5) Add the crystal control voltage difference ΔU to the current control voltage to adjust the local second pulse.

The timing device based on the GPS signal of the present invention includes a GPS receiving antenna, a GPS card, a phase detector, a CPU, a RAM, an EPROM, a D/A converter, a voltage-controlled crystal, a frequency multiplier and a frequency divider. The GPS card receives the satellite signal through the GPS antenna, recovers the GPS pulse from it and sends it to the phase detector, and the phase detector compares the GPS pulse recovered from the satellite signal with the local frequency division provided by the local frequency divider The phase difference of the pulse, the phase difference is sent to the CPU, the CPU stores the phase difference in the RAM, and after the RAM stores a certain amount of data, the CPU processes this batch of data to obtain the phase difference change value E and the phase difference change rate EC, look up the binary voltage control table stored in the EPROM according to the phase difference change value E and the phase difference change rate EC, and determine the crystal control for adjusting the voltage-controlled crystal The voltage difference ΔU is added to the voltage-controlled crystal through the D/A converter to adjust the output frequency of the voltage-controlled crystal. The output of the voltage-controlled crystal is sent to the frequency divider and the frequency multiplier at the same time, and the frequency divider produces the output of the timing device of the basic GPS signal of the present invention, and generates local frequency-divided pulses, and the multiplier The frequency converter generates a 65MHZ signal and sends it to the phase detector, uses the 65MHZ signal to count, and records the phase difference between the local frequency division pulse and the GPS pulse.

Because what the present invention adopted is three-stage crystal, therefore greatly reduced the cost of the present invention's equipment; Solved S.A interference and the frequency drift and the frequency jitter problem of voltage-controlled crystal preferably simultaneously by adopting the present invention's method, make the present invention's equipment The output accuracy can be compared with similar foreign equipment using high-quality crystals (above grade 2), and the test shows that the equipment of the present invention has achieved the following performance indicators:

Phase drift characteristics: Hundreds of seconds <50ns

                                                                                           

                                                              

Frequency characteristics: short-term (jitter) ≤5×10 ^-10

Long-term ≤5×10 ^-10

In addition, the device of the present invention does not need a large-capacity memory and a complicated crystal protection circuit, so that the circuit structure is simple, and when the GPS signal suddenly deteriorates and recovers after a period of time, the stored data can be updated quickly, so it can Quickly (about four minutes) a steady output is restored.

Embodiments of the present invention will be described below in conjunction with the accompanying drawings. In the attached picture:

Fig. 1 is the structural representation of an embodiment of the timing equipment of basic GPS signal of the present invention:

Fig. 2 is the flowchart of the timing method of basic GPS signal of the present invention;

Fig. 3 is the step S202 flow chart of fast capturing GPS second pulse frequency shown in Fig. 2;

Fig. 4 is the flowchart of step S206 of outputting precise frequency shown in Fig. 2;

Fig. 5 is a flow chart of constructing the voltage control table in the present invention.

Referring to Fig. 1, this figure shows that the timing equipment based on GPS signal of the present invention comprises: GPS receiving antenna 101, GPS card 102, phase detector 103, CPU104, RAM105, EPROM106, D/A converter 107, voltage-controlled crystal 108 , frequency multiplier 109, and frequency divider 110. Described GPS card 102 (the VPONCORE that Motorola Company produces in the present embodiment, provides second pulse SP once per second) receives satellite signal by described GPS antenna 101, recovers GPS second pulse therefrom and sends described phase detector 103 , the phase detector 103 compares the phase difference between the second pulse SP recovered from the satellite signal and the 1HZ signal provided by the local frequency divider 110, and sends the obtained phase difference to the CPU 104, and the CPU 104 stores the phase difference In the RAM105, after the RAM is full of a certain amount of data, the CPU processes the batch of data to obtain the phase difference change value E and the phase difference change rate EC, and searches for one stored in the EPROM106 according to E and EC to change the phase difference value and phase difference change rate of the binary voltage control table of the independent variable (the generation of this table will be described in detail later in conjunction with FIG. The converter 107 adds ΔU to the voltage-controlled crystal 108 to adjust the output frequency of the voltage-controlled crystal 108; the CPU also communicates with the GPS card to set the status parameters of the GPS card and read them from the GPS card Get information such as whether the satellite signal is normal or not. The output of the voltage-controlled crystal is sent to the frequency divider 110 and the frequency multiplier 109 simultaneously, and the frequency divider 110 produces signals of 2MHZ and 8MHZ as the output of the timing device based on GPS signals of the present invention, and Produce 1HZ signal as local second pulse, described frequency multiplier 109 produces 65MHZ signal and send to described phase detector 103, count with 65MHZ signal, record the phase difference of local second pulse and GPS second pulse, described RAM105 also according to the The instructions of the CPU store data such as phase difference change value and phase difference change rate. Programs necessary for the CPU 104 are stored in the EPROM 106 .

The timing method based on the GPS signal of the present invention needs to compare the phase difference between each GPS second pulse received and the local second pulse once per second, and store the phase difference, and perform the following specific steps as shown in Figure 2 simultaneously: first Complete the initialization work in step S201, including clearing the RAM, the initial operating voltage of the device crystal, and setting the number of phase differences M and N required to be stored. The number of phase differences reflects the time interval for adjusting the crystal control voltage. And M<N, the value of M is small to meet the requirements of quickly capturing the GPS second pulse frequency. Adjust the requirements of the voltage-controlled crystal, the best range is 30--180, then go to step S202: quickly capture the frequency of the GPS second pulse; then go to step S203: judge whether the satellite signal is normal, if judged as "No", Then step S201 is repeated after being reset in step S204; if step S203 is judged as "yes", then step S205 is executed: compare the phase difference between the newly received GPS second pulse and the local second pulse, and set this phase difference as the standard phase difference And store; Then go to step S206: enter the locked state, further adjust the local second pulse, and output the precise frequency; then judge whether the satellite signal is normal in step S207, if judged to be "yes", then return to execute step S206; as judged in step S207 For 'no', then proceed to step S208: keep the output obtained in step S206, and use the data stored before to adjust the crystal when needed, then judge whether the satellite signal is normal in step S209, as judged as 'No ', then return to step S208; if step S209 judges "Yes", then step S206 is executed. It needs to be explained that the data structures of several circular queues are set up in the present invention to store data such as the phase difference between the recorded GPS second pulse and the local second pulse, crystal voltage control difference, etc. When the queue is full, the first stored data It is automatically erased; the present invention stores about 8,000 GPS second pulses and local second pulse differences, and these data can be used to make special adjustments to the crystal under special circumstances such as abnormal satellite signals and strong S.A interference.

Fig. 3 shows the steps included in step S202 shown in Fig. 2: first in step S301 it is judged whether to store M phase difference values (M has been set in step S201), as judged as "no", then in step S301 Step S301 is executed after a delay of 1 second in step S203; if step S301 judges "Yes", then step S303 is directly executed: average the stored M phase difference values to obtain an average phase difference, and store the average phase difference; then execute Step S304: Judging whether M phase difference values have been stored, if the judgment is "No", then execute Step S304 after a delay of 1 second in Step S305; if the judgment is "Yes" in Step S304, then directly execute Step S306: Average the stored M phase difference values to obtain an average phase difference, and store the average phase difference; then proceed to step S307: compare the average phase difference obtained this time with the average phase difference stored last time to obtain the phase difference change value E; then Proceed to step S308: set phase difference change rate EC=0; Then in step S309 according to described phase difference change value E and phase difference change rate EC query voltage control table (the construction process of voltage control table will be described in conjunction with Fig. 5 description), obtain the crystal voltage control difference ΔU and store the difference; then perform step S310: add ΔU to the current control voltage, adjust the output frequency of the crystal; then perform step S311: judge whether the fast-catching process has been completed, If the judgment is "No", return to step S304; if the judgment is "Yes" in step S311, then enter step S203 shown in FIG. 2 .

Referring to Fig. 4, this figure shows the specific steps that step S206 shown in Fig. 2 comprises: at first judge whether to have stored N phase difference values (N has been set in step S201) in step S401, as judged as "No ", repeat step S401 after a delay of 1 second in step S402; if step S401 is judged as "yes", then directly execute step S403; average the stored N phase difference values to obtain an average phase difference, and store the average Phase difference; then execute step S404; compare the average phase difference obtained this time with the standard phase difference set in step S205 to obtain the phase difference change value E, then go to step S405; compare the average phase difference this time with the stored last time The average phase difference obtains the phase difference change rate EC (because in step S201 RAM is cleared, when executing step S405 for the first time, the 'average phase difference of the stored last time' is set to 0); then proceed to Step S406: Find out the crystal control voltage difference ΔU that should be applied according to the phase difference change value E, the phase difference change rate EC, and the pre-stored binary voltage control table with E and EC as independent variables; then execute step S407, and set ΔU It is added to the current control voltage to adjust the local pulse per second. It needs to be explained that before calculating the average phase difference in step S403, the stored phase difference value can be filtered to remove the data with large phase difference jitter.

Fig. 5 shows the flow chart of constructing the said binary voltage control table with said phase difference change value and said phase difference change rate as independent variables: first, the quantization range (-90ns～90ns) of phase difference change value E is defined in step S501 , and divide this range into X intervals (in this example, X is 13), then proceed to step S502: define the quantization range (-90ns～90ns) of the phase difference change rate EC, and divide this range into Y intervals ( In this example, Y is taken as 13), and then step S503 is executed: limiting the quantization range (-0.002V to 0.002V) of the crystal control voltage difference ΔU, and dividing the range into Z intervals (in this example, Z is taken as 13), Then in step S504, according to the formula ΔU=λ ₁ E+λ ₂ EC (where λ ₁ and λ ₂ represent the weighted values of E and EC) to determine the value of change corresponding to each pair of the phase difference E and the rate of change of the phase difference The crystal control voltage difference ΔU of the EC, that is, a binary voltage control table is obtained, and finally the binary voltage control table is stored in step S505.

Although the present invention has been described above in conjunction with the embodiments, it is obvious that the protection scope of the present invention is not limited thereto, and those skilled in the art may also make various obvious changes, for example: in step S309, the query binary voltage may not be used control table, and directly obtain the crystal voltage control difference ΔU according to the formula ΔU=λ ₁ E+λ ₂ EC; adopt GPS cards of other companies and models; The used RAM and/or EPROM can adopt other forms of data structures when storing data; the amount of data stored in the present invention can also be changed, the protection range of the M and N, and the phase difference change value, phase difference change rate, crystal Control the value range and division interval of the voltage difference, and so on. Therefore, the protection scope of the present invention is determined only by the claims.

Claims (16)

1. timing method based on gps signal, comprise each the GPS pulse of relatively receiving and the phase differential of local divided pulse, and store this phase differential, it is characterized in that according to effectively a data reserves N is set in filtering S.A. interference and the timely requirement of adjusting crystal, after being filled with N described differing, data are carried out smoothing processing, adjust described crystal, described to data carry out smoothing processing, the process of adjusting described crystal comprises following key step:

(1) calculates the mean value of N the described phase differential stored, obtain one and on average differ, and store this and on average differ;

(2) described on average differing with a predefined standard differed comparison, obtain differing changing value E;

(3) described on average the differing with last described on average differing of being stored that this is obtained compares, and obtains differing rate of change EC;

(4) differ changing value and the described rate of change that differs according to described, and deposit in advance differ changing value and the described rate of change that differs is that the crystal control voltage difference Δ U that should apply is determined in the binary voltages control table of independent variable with described;

(5) described crystal control voltage difference Δ U is added on the current control voltage, adjusts local pulse per second (PPS).

2. the timing method based on gps signal as claimed in claim 1 is characterized in that the step that makes up described binary voltages control table may further comprise the steps again:

-determine the described quantizing range that differs changing value E, and be several class with this scope division;

-determine the described quantizing range that differs rate of change EC, and be several class with this scope division;

-determine the quantizing range of described crystal control voltage difference Δ U, and be several class with this scope division;

-according to formula Δ U=λ ₁E+ λ ₂EC determines corresponding to each described changing value and the described described crystal control voltage difference Δ U that differs rate of change of differing promptly obtained the binary voltages control table as the Control of Voltage table;

This binary voltages control table of-storage.

3. the timing method based on gps signal as claimed in claim 1, it is characterized in that calculate described ask on average differ before, can carry out filtering to the described phase difference of storage earlier, remove and differ the bigger data of shake.

4. as claim 2 or 3 described timing methods based on gps signal, the span that it is characterized in that described N is 30～180.

5. the timing method based on gps signal as claimed in claim 4, it is characterized in that setting the described quantizing range that differs changing value is-90ns to 90ns, the described quantizing range that differs rate of change is-90ns to 90ns that the quantizing range of described crystal control voltage difference is-0.002V to 0.002V.

6. the timing method based on gps signal as claimed in claim 5, it is characterized in that with describedly differ changing value, the described quantizing range that differs rate of change, described crystal control voltage difference all is divided into 13 class.

7. as claim 1,2,3,5 or 6 described timing methods, it is characterized in that: store described phase differential and the described circle queue data structure that adopted when on average differing based on gps signal.

8. the timing method based on gps signal as claimed in claim 7, its feature also is: can utilize the described phase difference of being preserved to adjust crystal under special circumstances.

9. timing method based on gps signal, comprise each the GPS pulse of relatively receiving and the phase differential of local divided pulse, and store this phase differential, it is characterized in that according to effectively a data reserves N is set in filtering S.A. interference and the timely requirement of adjusting crystal, after being filled with N described differing, data are carried out smoothing processing, adjust described crystal, described to data carry out smoothing processing, the process of adjusting described crystal comprises following key step:

(1) calculates the mean value of N the described phase differential stored, obtain one and on average differ, and store this and on average differ;

(2) described on average differing with a predefined standard differed comparison, obtain differing changing value E;

(3) described on average the differing with last described on average differing of being stored that this is obtained compares, and obtains differing rate of change EC;

(4) by formula Δ U=λ ₁E+ λ ₂EC directly tries to achieve described crystal current pressure-controlled difference

(5) described crystal control voltage difference Δ U is added on the current control voltage, adjusts local pulse per second (PPS).

10. the timing method based on gps signal as claimed in claim 9, the span that it is characterized in that described N is 30～180.

11. the timing method based on gps signal as claimed in claim 10, it is characterized in that setting the described quantizing range that differs changing value is-90ns to 90ns, the described quantizing range that differs rate of change is-90ns to 90ns that the quantizing range of described crystal control voltage difference is-0.002V to 0.002V.

12. the timing method based on gps signal as claimed in claim 11, it is characterized in that with describedly differ changing value, the described quantizing range that differs rate of change, described crystal control voltage difference all is divided into 13 class.

13., it is characterized in that: store described phase differential and the described circle queue data structure that adopted when on average differing as claim 9,10,11 or 12 described timing methods based on gps signal.

14. the timing method based on gps signal as claimed in claim 13, its feature also is: can utilize the described phase difference of being preserved to adjust crystal under special circumstances.

15. the timing device based on gps signal comprises:

The antenna of-receiving satellite signal (101);

The GPS receiving circuit (102) of-recovery GPS pulse from satellite-signal;

-voltage-controlled crystal (oscillator) (108) and the frequency divider (110) of local divided pulse be provided;

The phase detector (103) of-comparison GPS pulse and local divided pulse phase differential;

The RAM (105) of-storage data;

-data are carried out smoothing processing, provided described crystal to control the CPU (104) of voltage difference;

-described crystal control voltage difference is added in D/A converter (107) on the described voltage-controlled crystal (oscillator) (108);

It is characterized in that this equipment also comprises:

-one storer (106) that is used for stored programme and described binary voltages control table.

16. the timing device based on gps signal as claimed in claim 15 is characterized in that: also comprise a frequency multiplier (109) that produces the 65MHz signal of the phase differential that writes down local divided pulse and GPS pulse.

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